public partial class OpaqueLayer : Panel

{

    private Color transparentBC = Color.SkyBlue;

    [Description("设置透明背景颜色")]

    public Color TransparentBC

    {

        get

        {

            return transparentBC;

        }

        set

        {

            transparentBC = value;

            this.Invalidate();

        }

    }

    //透明度

    private int alpha = ;

    [Description("设置透明度(0-255)")]

    public int Alpha

    {

        get  {  return alpha;  }

        set

        {

            if (value < )

            {

                value = ;

            }

            else if (value > )

            {

                value = ;

            }

            alpha = value;

            this.Invalidate();

        }

    }

    public OpaqueLayer()

    {

        InitializeComponent();

        //设置参数，使支持半透明、缓存、自行绘制

        SetStyle(ControlStyles.Opaque | ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint, true);

    }

    /// <summary>

    /// 自定义绘制窗体

    /// </summary>

    /// <param name="e"></param>

    protected override void OnPaint(PaintEventArgs e)

    {

        Graphics g = e.Graphics;            //获得绘图面板

        Color drawColor = Color.FromArgb(Alpha, TransparentBC);

        SolidBrush backColorBrush = new SolidBrush(drawColor);

        g.FillRectangle(backColorBrush, , , Width, Height);//绘制半透明

    }

    //该参数封装创建控件时所需的信息，必须重写该参数，以支持透明

    protected override CreateParams CreateParams

    {

        get

        {

            CreateParams cp = base.CreateParams;

            cp.ExStyle |= 0x20;  // 开启 WS_EX_TRANSPARENT,使控件支持透明

            return cp;

        }

    }

}